Serena Williams was seeded a lowly 28th for the 2011 US Open as tournament organisers opted to rigidly follow the current rankings rather than reward her for outstanding past performances.

Serena Williams was seeded a lowly 28th for the August 29-September 11 US Open as tournament organisers opted to rigidly follow the current rankings rather than reward her for outstanding past performances.

Williams, the dominant figure in women's tennis over the past decade, had already won the US Open three times but the former world number one's ranking tumbled after spending almost a year away from the game because of health problems.

The 29-year-old American returned to the courts in June and won back-to-back tournaments in California and Toronto to climb back to 29th in the world rankings after falling to 175.

She was bumped up one place for the US Open after last year's champion and world number three Kim Clijsters withdrew because of injury, but officials stopped short of elevating the 13-time grand slam champion much higher.

"After careful deliberation regarding Serena Williams' seeding, we decided to maintain the objective criteria in place to determine the women's singles seeds at this year's US Open," US Open tournament director Jim Curley said in a statement.

Although the US Open traditionally sticks with the world rankings, other grand slams have used their discretion to promote top players returning from injury.

At Wimbledon in June, Williams was elevated to seventh seed despite it being only her second tournament after a long layoff during which she suffered a foot injury and was diagnosed with life-threatening blood clots in her lungs.

Williams' sister Venus, a two-time US Open champion, was not seeded at all because her current ranking is 36th.

Denmark's Caroline Wozniacki, who has never won a grand slam but was a finalist at the US Open two years ago, was named top seed because she holds the number one ranking.

Russia's Vera Zvonareva, also chasing her first grand slam title after making the 2010 finals at Wimbledon and the US Open, was seeded second while former world number one Maria Sharapova was third.

Victoria Azarenka was fourth followed by Wimbledon champion Petra Kvitova, French Open champion Li Na and last year's French Open winner Francesca Schiavone.

The men's seedings were due to be released on Wednesday before both singles draws were made.